question about the noise!

Hi there.  

Now I study the flows which are driven by waves. When I carry out measurements of the velocity near the surface, the ADV  sometimes in and out of waters, which causes noise in the ADV outputs,so is the mean value of the noise zero?

If we deploy the ADV in air, is the mean value of the ADV outputs zero?

Thank for your consideration.I look foward to hearing from you.
 With best regards.
 Yours sincerely,
Zhenwei Zhang

Zhenwei,

When the Vector (I'm assuming this is what you are using) is in air, the velocity data will be quite noisy and the SNR and correlation will drop quite suddenly. The easiest way to identify when the Vector head is out of the water is to use SNR as it will typically drop to 5 dB or below.

P.J.

Thanks, I want to know whether the mean value of the noisy data equals to zero or not?

In theory, the noise you are seeing should be approximately white noise, so the mean should be zero (i.e. zero DC component). I don't know if this will be the case for your data set because the mean may not converge to its true value if the sample period (i.e. when the probe is out of the water) is not long enough.

P.J.

Thanks very much!